Electromagnetic interference (EMI) is a disturbance that affects an electrical circuit due to electromagnetic radiation. The disturbance may interrupt or otherwise degrade the performance of the circuit. Undesirable electromagnetic radiation often originates in integrated circuits (ICs) and is radiated by other structures at a level sufficient to cause interference with other components. A heatsink can be particularly problematic.
Heatsinks are used to redirect heat away from microchip surfaces. In the course of operation, energy from the microchip may capacitively couple to a heatsink. The energy may exit the heatsink as radiated EMI. Due to its large, metallic surface area, a heatsink may serve as an antenna for propagating electromagnetic radiation. A conventional attempt to reduce EMI includes extending drop points from a heatsink to logic ground to de-tune or shift the frequency of the electromagnetic radiation. While this technique may achieve EMI compliance, the drop points occupy scarce circuit board space that could be used for other circuit board functionality.